Cooling air and hot gas leakage between a hot gas path and cavities that contain cooling air in a gas turbine engine reduces engine performance and efficiency. For example, cooling air leakage from the cavities into the hot gas path can disrupt the flow of the hot gas and increase heat losses, thus reducing engine performance and efficiency. Further, cooling air leakage into the hot gas path requires higher primary combustion zone temperatures in the combustor to achieve desired engine firing temperatures. Moreover, hot gas leakage into the cavities leads to higher temperatures of components that are cooled with the cooling air from the cavities and may result in reduced performance, reduced service life and/or failure of these components.
In view of higher hot gas temperatures implemented in modern gas turbine engines, it is increasingly important to limit leakage between the hot gas path and the cavities to maximize engine performance and efficiency and to prevent damage to components that are cooled with the cooling air from the cavities.